Gas dryer desiccant and method of preparation



o. c. NORTON 3,390,511

GAS DRYER DESICCANT AND METHOD OF PREPARATION July 2, 1968 Filed Nov. 9,1965 a I I n u n I I I m n I z u I n I u u a m I n v p INVENT OR Or/o 6.Norton BY Wm (23% ATTORNEY United States Patent 3,390,511 GAS DRYERDESICCANT AND METHOD OF PREPARATION ()rlo C. Norton, Erie, Pa., assignorto Van Products Company, Erie, Pa., a corporation of PennsylvaniaContinuation-impart of application Ser. No. 434,167, Feb. 8, 1965. Thisapplication Nov. 9, 1965, Ser. No. 507,084

8 Claims. (Cl. 55-35) This application is a continuation in part ofpending United States patent application Ser. No. 434,167, filed byapplicant on Feb. 8, 1965, now abandoned for Gas Drier Desiccant andMethod of Preparation, which patent application in turn is acontinuation in part of United States patent application Ser. No.364,115 filed by applicant on Nlay 1, 1964, for Gas Drier Desiccant andApparatus Therefor, now abandoned, which patent application in turn wasa continuation in part of United States patent application Ser. No.268,608 filed by applicant on Mar. 28, 1963, for Gas Dryer, nowabandoned, with said latter patent application being a continuation inpart of United States patent application Ser. No. 96,974 filed byapplicant on Mar. 20, 1961, now abandoned, with said United Statespatent application Ser. No. 96,974 being a continuation in part ofUnited States patent application Ser. No. 678,227 filed by applicant onAug. 14, 1957, for Gas Dryer, now abandoned.

This invention relates to a desiccant and process for removing moisturefrom gases and especially air. The desiccant is a porous, granular solidwhich dissolves when contacted with moist air, and is utilized in theform of an air permeable bed positioned in the path of the moist air bya screen support or the like. In use, the desiccant bed dissolves andthe resulting liquid is collected in a sump beneath the screen support.

The present invention contemplates the use of a desiccant for removingmoisture from gases with the desiccant comprising a water soluble,substantially non-deliquescent porous carrier in pellet-like form,impregnated with a deliqucscent material. An example of the carrier orpellet material is sodium chloride and of the impregnating deliquescentmaterial calcium chloride. Moist air passing through a bed of suchimpregnated pellets is attracted by the deliquescent material (e.g. thecalcium chloride) which after sufficient contact with the moisturebecomes liquid. This liquid in turn dissolves the water soluble carriermaterial and the resulting solution fiows from the desiccant bed,leaving it efiicacious to further moisture removal.

The impregnating material used has a much greater aiiinity for waterthan the carrier material. The fact that this impregnating material isdeliquescent means that it liquefies upon exposure to sufficientmoisture before any of the carrier material goes into solution. Thus,the porous, granular water soluble carrier pellet remains almostentirely intact in its original form until dissolved by the liquidcreated within its pores and on its surface by the liquefication of theimpregnating material. The present invention provides the firstrecognition of the result obtainable by matching a deliquescentimpregnate material with a water soluble, porous, non-deliquescentgranular material, and is the first to obtain this result of completedissolution of a solid desiccant upon its continued exposure tomoisture. In terms of drying practice, the present invention providesthe first solid desiccant material that alleviates the problemassociated with prior art solid desiccants of removing desiccantresidues from a drying apparatus.

The desiccant material of this invention can be varied from neutral pHto acid or alkaline, but if the air drying apparatus coming into contactwith the material or its ICC solution is of a nature susceptible tocorrosion, the desiccant material should preferably be maintainedslightly alkaline. The desiccant material may be disposed in anapparatus connected to a compressed air system and also to an aftercooler, if lower dew points are desired. Containers utilizing thisimproved material can be also used to remove moisture from tank vents toprevent the entrance of atmospheric and entrained moisture when the tankbreathes, is emptied or filled. Oil, alcohol and gasoline storage tanksare examples of these applications.

An example of suitable drying apparatus in which the desiccant of thepresent invention can be used is the apparatus shown in United StatesPatent No. 2,642,951, issued June 23, 1953, to the present inventor, inwhich this desiccant can be employed as a bed of pellets constitutingbed (24) therein. In such apparatus, air enters the drier tank from thecompressor and preferably at a tangent or through a curved inlet at highvelocity, and because of the entrance in this manner, the air swirls ina circular fashion thereby throwing formed drops of oil, water or otherarticles suspended in the air outwardly or downwardly against the tankwall. These drops of liquid then gravitate to a sump at the bottom ofthe tank which can be drained as necessary. The swirled air then movesupwardly to and through the desiccant bed and through an outlet in thetank. During passage of the moist air through the desiccant pellets, theimpregnant absorbs the moisture and deliquensces, and because of theintimate contact of this first formed liquid with the surface and poresof the carrier material, the carrier also begins to dissolve. As thisdissolution continues, the resulant solution drips from the bottom ofthe screen or mesh-like support and down to the swirling air to collectin the bottom of the tank.

As the air progressively passes through the desiccant bed, the amount ofmoisture in this air becomes less and less. Thus only slight moisturereaches the pellets at and near the upper surface of the desiccant bed,and deliquescence does not occur initially in this upper area untilafter some use. Meanwhile, the pellets in the lower portion of the bedare dissolving away into solution which drops down into the sump.Additional fresh desiccant can be added to the top of the bed as may berequired.

At an inlet air temperature of approximately to F., a dew point of from10 to 0 degrees F. can be obtained by using calcium chloride as theimpregnant and sodium chloride pellets (e.g. water softener pellets)formed from the conventional cube-like crystals of sodium chloride, asthe carrier. Lower dew points can be achieved by lowering the ambienttemperature or with an after cooler connected between the compressor andthe drying apparatus.

An example of the improved desiccant which has been suocessfully usedfor general air drying purposes is by weight as follows:

Percent Sodium chloride NaCl (water softener pellets) -97 Calciumchloride CaCl 10-3 Sodium dichromate .01 Trisodium phosphate .01

. A specific example of the use of the above formulation 1s:

porous, granular, Water soluble carrier in pellet form. Calcium chlorideacts as the hygroscopic, deliquescent, impregnating material. Sodiumdichromate acts to prevent rust of the metal parts (it any) of thedrying apparatus, and also adds a pleasing color to the product.Trisodium phosphate is adapted to emulsify any Oll which may beentrained in the air stream.

If more than approximately of the hydroscopic deliques-cent impregnant,such as the calcium chloride, is used, the mass of pellets wouldtemporarily solidify due to excessive deliquescence, and drying actionWlll be not of peak efiiciency until the excess impregnant drips awayand the bed again becomes easily permeable by air. If less thanapproximately 1% of impregnant is used, the amount of deliquescencewould be generally inadequate to dissolve the water soluble carriermaterial at the proper rate of dissolution, to aid in removing moisturefrom the air or gas being dried. In short. the amount of deliquescentmaterial that is absorbed or impregnated into and onto the watersoluble, porous, granular carrier is that amount which provides foradequate dissolution of the resultant desiccant.

Other suitable carrier materials which may be utilized within the abovementioned range of 90% to 97% by weight, and which will act effectivelyfor use in providing the desiccant of the invention are as follows:

Other deliquescent impregnating materials which would be suitable forproducing the deliquescent desiccant of L the invention are as followsand as used within the above mentioned range of 10% to 3% Zinc chloridelllCl-p Lithium chloride .hiCl

The improved desiccant of this invention may be prepared as follows:

The carrier pellets may be of any desirable size. and preferably are ofa size of pellet of 14 inch to 't inch in any minimum dimension, withthe most desirable dimensions being between /2 inch and l inch. Suchcarrier pellets may be immersed in a saturated solution of thedeliquescent impregnating material, or the liquid impregnating materialcan be poured over the pellets. it is immaterial which procedure isfollowed because of the porosity of the carrier material. impregnationcan be done at room temperature but a more concentrated impregnation canbe achieved if the materials are heated.

In a specific process, sodium chloride pellets are heated to 400 to 600F. The impregnant, such as calcium chloride and/ or zinc chloride, andthe sodium dichromate and trisodium phosphate, all in water, are alsoheated to the boiling point of the resulting solution. The pellets maythen be immersed in this hot. saturated solution, and then removedtherefrom, and then placed in a tumbler and tumbled while cooling, tomaintain separation of the pellets. The resultant product is a hard,dry, impregnated and coated lump or pellet. Inorganic materials such asthe alkali metal chlorides are preferred as carrier materials if heatedimpregnation is used, as they are more stable at higher temperaturesthan organic materials such as the sugar and starch.

In a specific process using Sucrose pellets or tablets as the carrierand lithium chloride as the impregnant, a water solution of the lithiumchloride is heated to a temperature of approximately 250 F. and then thehot saturated solution is poured over the sugar pellets which are atroom temperature. The impregnated pellets may then be placed in an ovenpre-heated to 230 IR, and left there for a period of time (e.g., 45minutes after which they are re- 4 moved from the oven and cooled, as bymeans of a chilling device.

Referring now more specifically to the drawing, FIG. 1 shows adehydrator 10 comprising a tank 12 having a fill vent 11 with a suitablecover for replenishing the desicuant pellets 16. The liquid level ofwater removed from the air is shown at 14. This water may be drained offas at 24 at suitable intervals. An apertured partition 30 tlivides thetank into a sump 17 and the upper portion receiving the pellets 16. Thepartition 30 may include on its sides porous portions 15 which may be ofcoarse, tcreen mesh. The pellets 16 rest on top of the partition .llO.

.hn inlet opening 18 in the dehydrator tank 12 allows the air to passinto the dehydrator. The dehydrator could be used in an air line byconnecting an air inlet to the air inlet opening 18 and an outlet lineto the vent 20, which will allow air to flow into the tank through theopening 18 and up through the bed of pellets 16 to the outlet opening 20in a generally uniform pattern.

the partition in the embodiment illustrated is termed in the generalshape of the frustrum of a cone, having the outer periphery of the basethereof attached to the inner periphery of the tank 12. The chemicaldesiccant forming the bed of desiccant may take a generally naturalshape when poured into the tank, such as that thown in FIG. 1, which isroughly that of a cone as the tlesiccant material is added through thesupply opening ill.

in the embodiment illustrated in FIG. 2, the dehydrator has a tank 112which is shown with an inlet 132 and an outlet 120. The inlet 132 iscurved so that the air will take a downward swirling action andtherefore tend to throw out entrained water similar to the arrangementof FIG. I. Bafile 130 is a solid bafile with .a generally centralopening, and having the outer periphery of the ttaifle attached to theinside of the tank 112, as at 121. it batile 115 is a solid bafflehaving a solid center portion and being attached to the outer peripheryof the tank 110 at spaced points, so that the air can pass around thebafiie It15 as indicated by the arrows. A bafi'le 118 is generallytimilar to the bafile having a central opening therethrough.

Ttherefore, when the impregnated desiccant pellets are added to the tankthrough supply opening 111 and settle pn top of the batiie 118, they maytake the general shape of a cone, as shown, and a part thereof will fallthrough the central opening of the bafile 118 and rest on top of thecentral part of the baflle 115 as shown, and the air or gas will passthrough the bed 116 generally uniform as indicated by the arrows.Accordingly, the desiccant bed will absorb moisture from the air and theabsorbed moisture will go into solution as aforedescribed and fall downand accumulate in sump 117, as at 114. The drain 124 may be providedgenerally similar to that of drain 24 of the FIG. l embodiment.

tDbviously, many modifications and variations of the present inventionare possible in the light of the above teachings. it is therefore, to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

It claim:

1. A desiccant material for drying gas consisting essentially of aporous, water-soluble granular carrier in pellet-like form of sodiumchloride impregnated substantially only on the surface portions thereofwith calcium chloride, said sodium chloride being present in an amountof approximately 90% to 97% of the total weight of the tiesiccantmaterial and said calcium chloride being present in an amount ofapproximately 10% to 3% of the total weight of the desiccant material,said calcium chlotide upon exposure of the desiccant material to a gascontaining moisture being operative to absorb the moisture in the gasand to dissolve into liquid resulting in dissolving of the water-solublecarrier.

2. A desiccant material in accordance with claim 1 wherein saiddesiccant material contains a minor quantity of a material having rustinhibiting properties, in the order of approximately 0.01% of the totalweight of the desiccant material.

3. A desiccant material in accordance with claim 2 wherein said materialhaving rust-inhibiting properties consists essentially of sodiumdichromate.

4. A desiccant material in accordance with claim 1 wherein saiddesiccant material contains a minor quantity of a material which isoperative to emulsify oil in the gas, said oil emulsifying materialbeing in the order of approximately 0.01% of the total weight of thedesiccant material.

5. A desiccant material in accordance with claim 4 wherein said materialwhich is operative to emulsify oil consists essentially of trisodiumphosphate.

6. A method of dehydrating a gas containing moisture comprising passingsaid gas through a permeable bed consisting essentially of porous,water-soluble, pellets of sodium chloride, providing a carrierimpregnated substantially only on the surface portions thereof with adeliquescent material, said sodium chloride being present in in anamount of approximately 90% to 97% of the total weight of theimpregnated carrier, said deliquescent material consisting essentiallyof calcium chloride, in an amount of .approxmiately to 3% of the totalweight of the impregnated carrier, said deliquescent material beingoperative to dissolve into liquid upon exposure of the impregnatedpellets to the gas-containing moisture due to the absorbing of themoisture from the gas, and resulting in dissolving of the carrier.

7. A process for preparing a desiccant material for use in drying gascomprising, providing a porous, granular, generally water-solublecarrier of sodium chloride, heating said carrier to a temperature ofbetween approximately 400 F. to 600 F., heating a solution ofdeliquescent calcium chloride material to form a hot saturated solution,and then exposing said heated carrier to said hot saturated solution ofdeliquescent material to impregnate substantially only the surfaceportions of said carrier with said deliquescent material, said sodiumchloride being present in an amount of approximately 90% to 97% of thetotal weight of the desiccant material and said calcium chloride beingpresent in an amount of approximately 10% to 3% of the total weight ofthe desiccant material, and then drying said impregnated carrier bytumbling the impregnated carrier while the latter cools.

8. A process in accordance with claim 7 wherein said solution ofdeliquescent material is poured over said carrier material to exposesaid carrier material to said solution of deliquescent material.

References Cited UNITED STATES PATENTS 1,041,608 10/1912 Edeleanu 2521942,203,144 6/ 1940 Hammond 25 2l94 2,951,812 9/1960 Rapp 252-1942,967,154 l/l961 Beerman 252l94 2,988,509 6/1961 Schilberg -35 OTHERREFERENCES Gregory, T. C.: Uses and Application of Chemical and RelatedMaterials, Reinhold Publishing Co., 1939, pp. 624 and 625.

REUBEN FRIEDMAN, Primary Examiner.

SAMIH N. ZAHARNA, Examiner.

C. N. HART, Assistant Examiner.

1. A DESICCANT MATERIAL FOR DRYING GAS CONSISTING ESSENTIALLY OF APOROUS, WATER-SOLUBLE GRANULAR CARRIER IN PELLET-LIKE FORM OF SODIUMCHLORIDE IMPREGNATED SUBSTANTIALLY ONLY ON THE SURFACE PORTIONS THEREOFWITH CALCIUM CHLORIDE, SAID SODIUM CHLORIDE BEING PRESENT IN AN AMOUNTOF APPROXIMATELY 90% TO 97% OF THE TOTAL WEIGHT OF THE DESICCANTMATERIAL AND SAID CALCIUM CHLORIDE BEING PRESENT IN AN AMOUNT OFAPPROXIMATELY 10% TO 3% OF THE TOTAL WEIGHT OF THE DESICCANT MATERIAL,SAID CALCIUM CHLORIDE UPON EXPOSURE OF THE DESICCANT MATERIAL TO A GASCONTAINING MOISTURE BEING OPERATIE TO ABSORB THE MOISTURE IN THE GAS ANDTO DISSOLVE INTO LIQUID RESULTING IN DISSOLVING OF THE WATER-SOLUBLECARRIER.